Valve mechanism lift adjustment device and method

ABSTRACT

Rotating drive shaft is connected to a crankshaft and valve cam. Valve cam lifts intake and exhaust valves that are linked by a plurality of links. The amount of lift of intake and exhaust valves is adjusted by adjusting the position of a connector pin, that passes through two links and allows for their relative rotation. The adjustment of the connector pin is configured so that it is performed from single adjustment direction using prescribed adjustment tools.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a national stage application under 35 U.S.C.§ 371 based on International Application No. PCT/IB2005/003423, filed onNov. 15, 2005, and claims priority under 35 U.S.C. § 119 of JapanesePatent Application No. 2004-332623, filed on Nov. 17, 2004, the entirecontent of which is expressly incorporated by reference herein.

FIELD

The present invention relates to technology that adjusts the amount ofvalve lift of one of intake or exhaust valves through adjustment of theposition of a connector pin that connects two links of an internalcombustion engine valve mechanism.

BACKGROUND

Japanese Patent Publication No. 2001-123809 describes a lift andoperation angle varying mechanism that is one example of a variablevalve mechanism for internal combustion engines of automobiles and thelike, that can continuously modify intake or exhaust valvecharacteristics, i.e. valve lift amount and operation angle, to attainimprovements in fuel economy at low speeds and output at high speeds. Inthis mechanism, a rotating drive shaft connected to a crankshaft islinked by a plurality of links to oscillating cams that are valve cams,which lift intake and exhaust valves so that the lift characteristicsare changed by changing the position of the rocker arm, which is one ofthese links. In this kind of variable valve mechanism, variation in theamount of valve lift unavoidably occurs due to dimensional accuracyamong multiple link connection points. In particular, when the amount ofvalve lift (operation angle) is in the ultra-small lift region of 1 mmor less for example, air intake volume will fluctuate comparativelywidely due to small variations in the valve lift between cylinders, sothere is a possibility that engine operability and stability could behindered. Therefore, typical prior art mechanisms allow for theadjustment of the amount of the valve lift of intake and exhaust valvesby providing a variable valve mechanism comprised of specific links thatcan be selected and replaced from among a plurality of links ofdiffering dimensions and grades.

However, in this kind of method, the operation can sometimes beextremely difficult, depending on the position and direction of theportion of the adjustment tool that mates/inserts into the bolt. Ingeneral, there is limited space inside cylinder heads where many parts,such as valve mechanism links, are located, and therefore, if forexample, the portion of the adjustment tool that mates/inserts into thebolt is located inside a cylinder head, the adjustment tool must bemated/inserted without interfering with the surrounding parts inside thecylinder head, making this operation extremely difficult at times, oressentially impossible, hence requiring further improvements.

SUMMARY

The present invention takes these types of issues into consideration andallows for adjustment of the valve lift amount without disassembling thevalve mechanism by adjusting the position of the connector pin thatconnects two links comprising the valve mechanism, and has as its mainpurpose the achievement of adjustment time reduction and productivityimprovement through the further simplification/increase in efficiency(automation) of this kind of lift adjustment.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front elevation view that shows a lift/operation anglevarying mechanism as one embodiment of the valve mechanism to which thepresent invention applies.

FIG. 2 is an exploded perspective view that shows the pin connectionportion pertaining to one embodiment of the present invention.

FIG. 3 is a top view of the pin connection portion shown in FIG. 2.

FIG. 4 is a front elevation view of the same pin connection portionshown in FIG. 2.

FIG. 5 is a cross-sectional view along line axis A-A of FIG. 4.

FIG. 6 is a schematic diagram that shows the layout for the pinconnection portion in the engine-mounted condition.

FIG. 7 is a flowchart that shows the flow of the valve lift adjustmentprocess for the lift/operation angle mechanism.

FIG. 8 is an exploded perspective view that shows the pin connectionportion pertaining to the second working example of the presentinvention.

DETAILED DESCRIPTION

Next, a detailed explanation of the most favorable configuration for thepresent invention is provided with reference to the figures.

If the valve lift amount is not within a prescribed range when the valvelift is measured with the variable valve mechanism in the assembledcondition, the variable valve mechanism must be disassembled and thelink(s) replaced, and reassembled so adjustment operation man-hoursincrease and work efficiency is poor. In addition, concerns regardingadjustment accuracy remain because assembly error occurs easily duringlink reassembly.

Therefore, valve lift adjustment without replacement of links isdesirable. As one example of this, adjustment of the valve lift isconceivable by changing the position of a rotatable connector pin thatconnects to two links that comprise a variable valve mechanism. This canoccur, for example, by forming a pin guide hole to which the connectorpin could movably mate to one of the two links and the connector pincould be sandwiched and held by a pair of adjustable bolts. Whenadjusting the valve lift amount, the connector pin position would beadjusted by adjusting the bolts, using suitable adjustment tools such asa wrench, and by tightening the bolts after adjustment. Accordingly, thevalve lift adjustment is possible without disassembling the valvemechanism.

The present invention pertains to a lift adjustment device for a valvemechanism that has a rotating driveshaft connected to a crankshaft and avalve cam that contacts and lifts intake or exhaust valves, wherein thevalve mechanism is provided with a plurality of links that link thedriveshaft and valve cam; a connector pin inserted into and connectingtwo of the plurality of links enabling relative rotation of both; and ameans of lift adjustment in which the position of the connector pin isadjustable from a single direction using prescribed adjustment tools inorder to adjust the amount of lift of the intake and exhaust valves.

The present configuration allows for lift adjustment performed byadjusting the position of the connector pin in this manner, resulting inimproved work efficiency and adjustment accuracy without disassemblingthe valve mechanism to replace links as in the prior art describedabove. And, since the connector pin position adjustments performed byadjustment tools can be made from a single direction, there are fewlayout restrictions, and therefore adjustment operations can beperformed easily without concerns about interference between adjustmenttools and parts inside cylinder heads. Thus, automation of liftadjustment operations is achievable using a nut runner, or the like,provided as the adjustment tool, for example, and it is possible todramatically improve productivity through reductions in operation timeas well as improve adjustment accuracy through automatic adjustment.

Next, a detailed explanation of the most favorable configuration for thepresent invention is provided with reference to the figures. As afavorable example of a valve mechanism applied in this invention, FIG. 1shows lift/operation angle varying mechanism 10 that can continuouslyvary both the intake valve lift amount and the operation angle byopening and closing the intake valves.

Lift/operation angle varying mechanism 10 is comprised of a plurality oflinks that link rotating drive shaft 11 connected to a crankshaft, andoscillating cam 13 mated to drive shaft 11 such that the cam canoscillate and lift the intake valve. In short, lift/operation anglevarying mechanism 10 is provided with eccentric drive portion 12 locatedeccentrically to drive shaft 11, control shaft 14 extending in thecylinder row direction parallel to drive shaft 11, eccentric controlshaft portion 15 located eccentrically to the control shaft 14, rockerarm 16 mated to the eccentric control shaft portion 15 such that therocker arm can oscillate, ring-shaped first link 17 that links eccentricdrive shaft portion 12 and one end of rocker arm 16 and second link 18that links the other end of rocker arm 16 and the front end ofoscillating cam 13. First link 17 is mated so that it can rotate in thecircular periphery of eccentric drive shaft portion 12. One end ofrocker arm 16 and the front end of first link 17 are rotatably connectedby first connector pin 21. The other end of rocker arm 16 and one end ofsecond link 18 are rotatably connected by second connector pin 22. Theother end of second link 18 and the front end of oscillating cam 13 arerotatably connected by third connector pin 23.

Drive shaft 11 is connected to a crankshaft via a transmission mechanismnot shown in the figure such as a chain or a pulley and movesrotationally connected to the crankshaft. Also, as shown in FIG. 6,drive shaft 11 extends in the cylinder row direction (perpendicular tothe paper surface of FIG. 6) and is rotatably supported above cylinderhead 2. Cylinder head 2 is comprised of head lower 2A, which sandwichesand holds rotatable drive shaft 11, and ladder-frame shaped head upper2B, which consists of a plurality of integrated bearing caps and isfixed to the upper surface of head lower 2A. Further, drive shaft 11 andcontrol shaft 14 are provided for a cylinder row comprised of aplurality of cylinders and are shared by all cylinders comprising thecylinder row. With respect to this, component parts 12, 13 and 15through 23 for lift/operation angle varying mechanism 10 are providedfor each of the cylinders that comprise the cylinder row.

Referring again to FIG. 1, oscillating cam 13, acting as a valve cam, islocated above valve lifter 1A of each cylinder's intake valve 1. Similarto drive shaft 11, rotatable control shaft 14 is supported by cylinderhead 2, and in addition, its rotation angle position is changed andmaintained by operation angle actuator 19.

In terms of a brief explanation of the operation of this lift/operationangle varying mechanism 10, when driveshaft 11 is rotated, rocker arm 16oscillates via eccentric drive shaft portion 12 and first link 17, theoscillation motion of this rocker arm 16 is transmitted via second link18 to oscillating cam 13, and oscillating cam 13 oscillates. Oscillatingcam 13 contacts valve lifter 1A provided above intake valve 1, and bypressing against this valve lifter 1A, intake valve 1 opens and closes,or in other words, lifts against the valve spring reactive force.

In addition, changing the rotational position of control shaft 14 bymeans of operation angle actuator 19 will change the center position ofeccentric control shaft portion 15, which is the oscillation supportpoint of rocker arm 16. By doing this, the range of oscillation foroscillating cam 13 varies, while the center phase of the operation angleof intake valve 1 remains nearly steady in relation to the crank angle(crankshaft rotational position). The size of the valve lift for intakevalve 1 (maximum lift) and the operation angle will both varycontinuously and smoothly (not in stages). The control status of thislift/operation angle varying mechanism 10 is detected, for example, by acontrol shaft sensor (lift sensor), which is an angle sensor thatresponds to the rotational position of control shaft 14.

This kind of lift/operation angle varying mechanism 10 enablescontinuous change of both valve lift and operation angle of intake valve1 and provides the following kinds of unique interaction effects. Sincemost connecting points of each link element are surface contacts,lubrication is easy, and reliability and durability are superior.Because there is no need to use a biasing means such as return springs,the configuration is simple, and reliability and durability aresuperior. In addition, this mechanism 10 can be easily applied withoutmajor changes to layout with respect to internal combustion engines withdirect acting valve systems because drive shaft 11 and oscillating cam13 can be located in almost the same position as a preexisting directacting valve system camshaft and fixed cam.

Furthermore, by using this kind of lift/operation angle varyingmechanism 10, intake air volume can be widely adjusted without relianceon a throttle valve by using valve lift amounts in an extremely smalllift range of 1 mm or less, for example, whereby so-called throttle losscan be greatly reduced or eliminated. However, in this kind of extremelysmall lift range, it is very important to accurately adjust the valvelift amount within a prescribed dimensional tolerance to effectivelyreduce or eliminate variation in the amount of valve lift betweencylinders, because a miniscule amount of variation in valve lift betweencylinders will result in comparatively large variation in intake airvolume.

The amount of valve lift is adjusted in the present working example byadjusting the position of second connector pin 22 that connects secondlink 18 and rocker arm 16 that are the two links comprising thelift/operation angle varying mechanism 10.

FIGS. 2 through 5 show the pin connection portion of rocker arm 16 andsecond link 18 pertaining to the first working example of the presentinvention. Rocker arm 16 is comprised of main bearing portion 31 intowhich is rotatably mated eccentric control shaft portion 15, first pinmating portion 32 where first pin 21 mates and second pin mating portion33 where second pin 22 mates, and items 31 through 33 are formed as oneintegrated piece with an appropriate metal material. The two pin matingportions 32 and 33 are formed ancillary to the outer periphery of mainbearing portion 31, and in addition, are mutually offset in the axialdirection of main bearing portion 31 to avoid interference.

In second pin mating portion 33 is formed pin guide hole 35 into whichis movably mated first connector pin 22 along prescribed adjustmentdirection 34 in the radial direction of second connector pin 22. Inshort, pin guide hole 35 is penetration-formed in the axial direction ofconnector pin 22 so that it also forms a long slot in the adjustmentdirection 34.

The position of connector pin 22 is changed and maintained in adjustmentdirection 34 by a pair of holders, first holder 36 and second holder 37,that sandwich and hold connector pin 22 in the adjustment direction 34.Holder mating holes 38 and 39 into which holders 36 and 37 respectivelymate are formed at pin mating portion 33. Each of holder mating holes 38and 39 is formed along the adjustment direction 34, and in addition, oneend of each opens to pin guide hole 35. Threaded portions are formed onthe outer surfaces of holders 36 and 37 and the inner surfaces of holdermating holes 38and 39 that screw together. As described below,bolt-shaped holders 36 and 37 are turned with socket wrench 41 and hexwrench 42 used as adjustment tools (see FIG. 1), and the position ofconnector pin 22 is adjusted by loosening or tightening holders 36 and37 through the threaded portions.

On first holder 36 at the edge of the opposite side of pin guide hole 35is formed bolt head 43 as the first tool mating portion that mates tosocket wrench 41, which is used as the first adjustment tool that turnsfirst holder 36. Bolt head 43 has a polygonal shape such as thehexagonal shape pictured. On second holder 37 is formed tool mating hole44 as a second tool mating portion that mates to hex wrench 42, which isused as the second adjustment tool that turns second holder 37. Thistool-mating hole 44 is an elongated hole with a hex-shaped cross-sectionthat matches hex wrench 42, and the hole 44 extends in the adjustmentdirection with one end opening to the end of pin mating hole 35.Furthermore, tool insertion holes 45 and 46 that enable insertion of thehex wrench are penetration-formed in first holder 35 and connector pin22. These tool insertion holes 45 and 46 are set with a larger diameterthan hex wrench 42 and tool-mating hole 44.

Seat surface 47, whose surface comes into contact with flat end surfacesof holders 36 and 37, are formed on the periphery of connector pin 22 sothat these tool insertion holes 45 and 46 are arranged on the same axisline in adjustment direction 34, in other words, in order to locate therotational position of the connector pin with respect to pin matingportion 33; and in addition, a locator slot 48 is formed on theperiphery of connector pin 22 to check and adjust the rotationalposition of connector pin 22. Reference symbol 49 is an oil hole forsupplying lubrication oil to the bearing surface of main bearing portion31.

In second link 18, two-pronged portion 18B is formed by pin holes 18A,which are rotatably mated to connector pin 22; pin mating portion 33 isplaced between two-pronged portion 18B; and by inserting connector pin22 into pin holes 18A and the pin guide hole 35, second link 18 androcker arm 16 become rotatably connected.

Since connector pin 22 is securely fixed and held to pin mating portion33 by holders 36 and 37 when assembled, as illustrated in the secondembodiment shown in FIG. 8, which is explained below, a retaining headand flange that protrude further than the axial direction of second link18 are not provided at both ends of connector pin 22 so that both endsof connector pin 22 are positioned nearly flush with side surfaces ofsecond link 18, resulting in reduction of weight and size.

FIG. 7 is a flow chart showing the valve lift adjustment procedure forthe valve mechanism 10. In step 1 (“step” is abbreviated as “S” in thefigure), the amount of valve lift of the plurality of cylinderscomprising a cylinder row is measured. Specifically, the amount of valvelift of each cylinder is measured with each component part of valvemechanism 10 in the assembled condition.

Next, in step 2, control shaft 14 is set in a prescribed minimum liftposition, and drive shaft 11 is set in a prescribed rotational positionwherein all cylinders comprising a cylinder row have essentially nolift. Also, when the maximum valve lift amount is essentially 0 (“zero”)at the minimum lift position, the valve lift amount of all cylinderswill be 0; regardless of the rotational position of the drive shaft. Instep 3, first holder 36 is loosened with socket wrench 41. In step 4,based on the measurement results from step 1, second holder 37 is turnedby hex wrench 42, the position of connector pin 22 is adjusted, and theamount of valve lift is adjusted. In step 5, first holder 36 istightened with socket wrench 41, and the position of connector pin 22 isfixed and held in the post-adjustment position. Next, in step 6, theamount of valve lift is measured again to confirm that the adjustmentwas done correctly. If the adjustment is insufficient, theaforementioned adjustment operation is repeated. The series ofadjustment operations is completed when the correct adjustment has beenconfirmed. This type of series of adjustment operations is automated bya nut runner, or the like, that provides socket wrench 41 and hex wrench42 on the same axis so adjustment operations can be performed accuratelyand efficiently in a short amount of time.

In the present working example, the adjustment of the position ofconnector pin 22 using adjustment tools 41 and 42 is performed in thesame, single direction, or adjustment direction 34. Specifically, thedirection in which socket wrench 41 mates with head portion 43 of firstholder 36, and the direction in which hex wrench 42 is inserted intoopening 45A of tool insertion hole 45 are set on the same axis linealong adjustment direction 34.

FIG. 8 shows an adjustment device pertaining to the second workingexample of the present invention. The second working example variesgreatly from the first working example in that bearing 60 is providedthat rotatably supports connector pin 22. The structures in common withworking example 1 bear the same reference symbols, so duplicateexplanation is omitted accordingly. Bearing 60 has a halved structurewherein each half part 61 and 62 is placed between holders 36 and 37 andconnector pin 22, rotatably supports connector pin 22 and movably matesinto pin guide hole 35 with connector pin 22 in adjustment direction 34.In each half part 61 and 62, tool insertion holes 61 A and 62A arepenetration-formed, through which hex wrench 42 is inserted, similar tothe tool insertion holes 45 and 46. Also, to prevent connector pin 22from becoming detached, large diameter head portion 22A is formed on oneend of connector pin 22, and on the other end 22B, a large diameterflange (not shown in the Figure) is mated. Washer-shaped leaf springs 64are inserted between both ends of bearing 46 and the sides of the secondlink in an axial direction.

The characteristic structures and effects of the working examplesrelated to the present invention are listed below.

The present invention is comprised of a valve mechanism (10) connectedby a plurality of links, 16 through 18, to valve cam 13 that contactsand lifts intake/exhaust valves and rotating drive shaft 11 connected toa crankshaft. It is also comprised of connector pin 22, inserted intotwo of the plurality of links 16 through 18 (16, 18) comprising thisvalve mechanism 10 and enables their relative rotation, and a liftadjustment means to adjust intake and exhaust valve lift amount whereinthe position of connector pin 22 is adjustable from a single direction(adjustment direction 34) using prescribed adjustment tools 41 and 42.

Since lift adjustment operations performed by adjusting the position ofthe connector pin in such a manner eliminate the need to disassemble thevalve mechanism in order to adjust the lift, as in the aforementionedprior art, operation man-hours and time are greatly reduced, andadjustment accuracy is also superior. In addition, adjustment of theposition of connector pin 22 using adjustment tools 41 and 42 can bemade from single adjustment direction 34. In other words, the mating andinsertion direction of both adjustment tools 41 and 42 are set in thesame adjustment direction 34. Therefore, as described below, byproviding adjustment tools 41 and 42 that can easily be inserted andmated in adjustment direction 34 without interfering with surroundingparts, the previously described series of adjustment operations can beautomated through a nut runner set up on the same axis as socket wrench41 and hex wrench 42, which are used as adjustment tools; adjustmentaccuracy improves through automatic adjustments; and in addition,operation man-hours and time are greatly reduced and operationefficiency and productivity can be dramatically improved.

Hypothetically speaking, if the adjustment directions based on theadjustment tools, namely, insertion and mating directions, weredifferent, it would be extremely difficult to set both of the adjustmentdirections so that insertion and mating of both of the adjustment toolscould be done easily without interfering with surrounding parts, and itwould be very difficult to automate adjustment operations as shown inthe present working examples.

Generally in drive mechanisms, drive shaft 11, rotatably supported abovecylinder head 2, is provided as a cylinder row comprised of a pluralityof cylinders, and valve mechanism 10 is provided for each of theplurality of cylinders that comprise a cylinder row. Thus, depending onthe rotational position of drive shaft 11, the position and orientationof adjustment direction 34 will vary at the plurality of cylinders thatcomprise the cylinder row.

FIG. 6 is a schematic diagram that shows the entire connector pin 22vicinity of each of the drive mechanisms provided for each of fourcylinders comprising a cylinder row, with drive shaft 11 set in theprescribed rotational position, as shown in step 2 of FIG. 7, in otherwords, in the condition to carry out the position adjustment ofconnector pin 22 as shown in steps 3 through 5 of FIG. 7. As shown inthe same figure, the section where adjustment tools 41 and 42 are matedand inserted for all cylinders comprising a cylinder row, specifically,bolt head portion 43, to which socket wrench 41 mates, and opening 45Aof tool insertion hole 45, into which hex wrench 42 is inserted, arepositioned higher in the engine (toward the top of FIG. 6) than uppersurface 2C of cylinder head 2 (head upper 2B). In other words, when infull operation, tool mating/insertion portions 43, 45A are configured sothat they are not positioned below the upper surface 2C of cylinder head2.

There are numerous parts inside cylinder head 2 positioned below uppersurface 2C of cylinder head 2, such as links, that comprise valvemechanism 10, and since there is limited space, hypothetically speaking,if portions 43 and 45A, where adjustment tools mate and are inserted,intrude inside the cylinder head below upper surface 2C of cylinder head2, operations to mate and insert adjustment tools in this portion willbecome difficult, and automatic lift adjustment may no longer bepossible. Due to this, since in the working example, portions 43 and45A, where adjustment tools mate and are inserted, are positioned aboveupper surface 2C of cylinder head 2 where there is comparatively moreroom, the automatic lift adjustment can be reliably achieved with valvemechanism 10 in the assembled engine-mounted condition in an internalcombustion engine.

In other words, single adjustment direction 34, which is the directionof insertion of tools 41 and 42, is provided in a range such that thedirection is oriented essentially from upper engine to lower engine atall cylinders comprising a cylinder row. Thus, the automatic liftadjustment can be reliably achieved because adjustment tools 41 and 42can be inserted and mated from above cylinder heads, where there is moreroom, without encountering interference with surrounding parts.

As a specific example of adjustment from a single direction using theadjustment tools, pin guide hole 35 is formed for connector pin 22,which is movably mated in prescribed adjustment direction 34 along theradial direction at pin mating portion 33 on one of the two links. Theposition of connector pin 22 is adjusted by adjusting a pair of holders,first holder 36 and second holder 37, that sandwich and hold connectorpin 22 in the adjustment direction 34. Also, the configuration is suchthat positional adjustment of first and second holders 36 and 37 isperformed from a single direction, or adjustment direction 34.

More specifically, first and second holder mating holes 38 and 39 areformed that extend along the adjustment direction at pin mating portion33, with one end of each open to the pin mating hole 35, and into whichthe first and second holders 36 and 37 are screwed. First tool matingportion 43 is formed at one end of first holder 36 to which firstadjustment tool 41, such as a socket wrench, mates and rotates firstholder 36. Second tool mating portion 44 is formed at one end of secondholder 37 to which second adjustment tool 42, such as a hex wrench,mates and rotates second holder 37. Tool insertion holes 45 and 46 arepenetration-formed to allow the second adjustment tool 42 to be insertedthrough the first holder 36 and connector pin 22.

According to the configurations described above, the position of theconnector pin can be adjusted with a relatively simple structure thatuses two holders (bolts) 36 and 37, thus allowing for a reduction insize and weight, higher reliability and easier assembly operations.

Preferably, as in the second working example shown in FIG. 8, a bearing60 is provided, located between holders 45 and 46 and connector pin 22,that rotatably supports the connector pin 22 and at the same time mateswith pin guide hole 35 and is moveable in adjustment direction 34together with the connector pin 22. In this case, since connector pin 22can be moved in the adjustment direction while being rotated axially bybearing 60, the pin connection portion of connector pin 22 can have aso-called full-floating connection structure, allowing for improved wearresistance and reliability.

A typical example of the varying mechanism is lift/operation anglevarying mechanism 10 that can continuously change the valve lift andoperation angle of intake and exhaust valves. This lift/operation anglevarying mechanism 10 is provided with an eccentric drive shaft portion12 located eccentrically to drive shaft 11, control shaft 14, eccentriccontrol shaft portion 15 located eccentrically to control shaft 14,rocker arm 16 rotatably supported by eccentric control shaft portion 15,first link 17 that links one end of the rocker arm and the eccentricdrive shaft portion, second link 18 that links the other end of rockerarm 16 and the valve cam 13, and actuator 19 that changes and maintainsthe rotational position of control shaft 14 to adjust the liftcharacteristics of the intake and exhaust valves. The present inventionapplies to connector pin 22, which is rotatably connected to rocker arm16 and second link 18, for example.

By using this kind of lift/operation angle varying mechanism 10, intakeair volume can be adjusted without reliance on a throttle valve becausevalve lift and operation angle of intake and exhaust valves can becontinuously adjusted, and throttle loss can be greatly reduced oreliminated. On the other hand, miniscule variation in the amount of liftbetween cylinders tends to cause relatively large fluctuations in intakeair volume, particularly when valve lift amounts are in an extremelysmall lift range. Therefore, it is very important to adjust theaforementioned lift amount within prescribed dimensional tolerances.

The lift adjustment method pertaining to the present invention ischaracterized by step 1 in which the valve lift amount is measured withthe valve mechanism in the assembled state, and steps 2 through 4 inwhich, based on the results of the valve lift measurement, drive shaft11 is set in a prescribed rotational position and intake and exhaustvalve lift amounts are adjusted by adjusting the connector pin positionfrom a single direction using prescribed adjustment tools.

The present invention has been explained based on specific workingexamples, but it is not limited to the working examples, and includesvarious modifications and alterations that do not fall beyond the scopeof its intent. For example, the aforementioned working examples apply toa valve mechanism at the intake air valve side, but the presentinvention could also apply to a valve mechanism at the exhaust valveside. In addition, the working examples apply the present invention toan in-line 4 cylinder internal combustion engine, but the presentinvention can also be applied to other types of multiple cylinderinternal combustion engines, such as in-line or V-type 6 cylinder and 8cylinder engines and the like.

CONCLUSION

Although specific embodiments have been illustrated and describedherein, it will be appreciated by those of ordinary skill in the artthat any arrangement, which is calculated to achieve the same purpose,may be substituted for the specific embodiment shown. This applicationis intended to cover any adaptations or variations of the presentinvention. Therefore, it is manifestly intended that this invention belimited only by the claims and the equivalents thereof.

1. A lift adjustment device for a valve mechanism connected by aplurality of links to a valve cam that contacts and lifts intake/exhaustvalves and a rotating drive shaft connected to a crankshaft, the devicecomprising: a connector pin, inserted into two of the plurality oflinks, that connects both links and allows for their relative rotation;a lift adjustment means wherein the connector pin position is adjustablefrom a single direction using a prescribed adjustment tool; and a pinguide hole into which the connector pin, which is radially moveable in aprescribed adjustment direction, mates at a pin mating portion on one ofthe two links; and the lift adjustment means that is provided with apair of holders, first holder and second holder, that sandwich and holdthe connector pin in the prescribed adjustment direction, with theposition of the connector pin being adjusted by adjusting the firstholder and second holder wherein a configuration in which positionaladjustment of the first holder and second holder is performed from thesingle direction.
 2. The valve mechanism lift adjustment devicedescribed in claim 1, wherein the drive shaft is rotatably supportedabove cylinder heads and provides for each cylinder row, comprised of aplurality of cylinders, and the valve mechanism provided for each of theplurality of cylinders that comprise a cylinder row such that portionsinto which the adjustment tools mate or are inserted into a link are setat a position that is higher than an upper surface of the cylinder headsfor all cylinders comprising a cylinder row, at least when the driveshaft is in a prescribed rotational position.
 3. The valve mechanismlift adjustment device described in claim 2 wherein the drive shaftprovided for a cylinder row, comprised of a plurality of cylinders andthe valve mechanism provided for each of a plurality of cylinders thatcomprise a cylinder row wherein the single direction provided such thatthe direction is oriented essentially from upper engine to lower enginefor all cylinders comprising a cylinder row, at least when the driveshaft is in a prescribed rotational position.
 4. A lift adjustmentdevice for a valve mechanism connected by a plurality of links to avalve cam that contacts and lifts intake/exhaust valves and a rotatingdrive shaft connected to a crankshaft, the device comprising: aconnector pin, inserted into two of the plurality of links, the connectsboth links and allows for their relative rotation; a lift adjustmentmeans wherein the connector pin position is adjustable from a singledirection using a prescribed adjustment tool; first and second holdermating holes that extend along an adjustment direction at a pin matingportion, with an end open to a pin guide hole, and into which the firstand second holders are screwed; a first tool-mating portion formed atone end of the first holder to which first adjustment tool mates andturns the first holder; and a second tool-mating portion formed at oneend of the second holder to which second adjustment tool mates and turnsthe second holder wherein tool insertion holes penetration-formed toallow the second adjustment tool to be inserted through the first holderand the connector pin.
 5. The valve mechanism lift adjustment devicedescribed in claim 4 and further comprising a bearing, placed betweenthe holders and connector pin, that rotatably supports the connectorpin, and at the same time mates with the pin guide hole and is moveablein the adjustment direction together with the connector pin.
 6. A liftadjustment device for a valve mechanism connected by a plurality oflinks to a valve cam that contacts and lifts intake/exhaust valves and arotating drive shaft connected to a crankshaft, the device comprising: aconnector pin, inserted into two of the plurality of links, thatconnects both links and allows for their relative rotation; and a liftadjustment means wherein the connector pin position is adjustable from asingle direction using a prescribed adjustment tool; an eccentric driveshaft portion located eccentrically to the drive shaft, a control shaft,an eccentric control shaft portion located eccentrically to the controlshaft, a rocker arm rotatably supported to the eccentric control shaftportion, a first link that links one end of the rocker arm and theeccentric drive shaft portion, a second link that links the other end ofthe rocker arm and the valve cam, and an actuator that changes andmaintains the rotational position of the control shaft to adjust thevalve lift characteristics of the intake and exhaust valves wherein theconnector pin is rotatably connected to the rocker arm and the secondlink.
 7. A lift adjustment device for a valve mechanism connected by aplurality of links to a valve cam that contacts and moves intake/exhaustvalves and a rotating drive shaft connected to a crankshaft, the devicecomprising: a connector pin, insertable into a first and a second linkof the plurality of links, that connects both links and allows for theirrelative rotation, the connector pin having an opening; a threaded firstholder that is insertable into a first threaded hole of the first linkunder and immediately adjacent to the connector pin, the first holderhaving an opening adapted to accept an adjustment tool, the first holderopening substantially aligning with the connector pin opening when thefirst holder is screwed into the first threaded hole; and a threadedsecond holder comprising an opening that extends the length of thesecond holder, the second holder insertable into a second threaded holeof the first link above and adjacent to the connector pin such that thesecond holder opening aligns with the connector pin opening and thefirst holder opening allowing insertion of the adjustment tool throughthe second holder.
 8. The lift adjustment device described in claim 7wherein the adjustment tool is adapted to turn the first holder withinthe first threaded hole to adjust the connector pin position in thefirst link thereby changing a position of the second link with respectto the first link.
 9. The lift adjustment device described in claim 7wherein the connector pin is movable in a first direction in the firstlink but substantially immovable in the first direction in the secondlink.
 10. The lift adjustment device described in claim 7 wherein thesecond holder is adapted to be screwed into the second threaded hole tocontact the connector pin after lift adjustment has been made.
 11. Thelift adjustment device described in claim 7 wherein the connector pinfurther comprises a first seat surface that contacts the first holderand a second seat surface that contact the second holder.
 12. The liftadjustment device described in claim 7 wherein the first link furthercomprises a bearing portion into which a control shaft portion can berotatably mated.
 13. The lift adjustment device described in claim 12wherein the bearing portion further comprises an oil hole for admittinglubrication for the bearing surface.
 14. The lift adjustment devicedescribed in claim 7 wherein the threaded second holder furthercomprises a bolt head that is adapted to be turned by a wrench.
 15. Thelift adjustment device described in claim 7 wherein the first holder isadapted to be screwed further into the first link, in response to theadjustment tool, to move the connector pin in a first direction in thefirst link.